2001 TJ 2.5 sputters at idle and dies

[NoleyPoley807]

Hey all.

I recently purchased a 2001 TJ 2.5l and was told it needed a fuel pump as it would randomly studder under load.

I replaced the fuel pump and both O2 sensors (NTK) last weekend. I decided to drive it Tuesday morning and it ran completely fine, parked for about an hour and then ran completely fine again to the next destination. No studder, idled fine, etc.

After work I went out to crank it and it immediately started spitting and studdering at idle and died. It did that multiple times so I ran it up to about 2k rpm's and the studdering stopped unless it went down to idle. I drove it home while keeping the rpm's up and luckily made it.

I performed a fuel pressure test and it jumps right up to 40-45lbs and leaks down if I don't crank it. Once I crank it, it stays around 40-50lbs at idle or when giving gas. At idle it just dies again.

Any help would be much appreciated.

 

[macleanflood]

Try reading live ODB data and see where your fuel trims and O2 voltages are at. A $30 Bluetooth dongle and Torque Lite will do that.

Check and make sure your intake is tight. Clean your IAC. Check for vacuum leaks.

Might want to try running it without the downpipe (front) O2 to rule out a plugged CAT.

-Mac

 

[KennethS]

Have you checked for any fault codes? Many auto parts stores will scan your vehicle for free.

 

[NoleyPoley807]

 

[NoleyPoley807]

View attachment 606494

 

[NoleyPoley807]

Try reading live ODB data and see where your fuel trims and O2 voltages are at. A $30 Bluetooth dongle and Torque Lite will do that.

Check and make sure your intake is tight. Clean your IAC. Check for vacuum leaks.

Might want to try running it without the downpipe (front) O2 to rule out a plugged CAT.

-Mac

Now after running it at 2k rpm's for about 5 minutes it shows no errors and is idling fine.

 

[NoleyPoley807]

Now after running it at 2k rpm's for about 5 minutes it shows no errors and is idling fine.

 

[NoleyPoley807]

Try reading live ODB data and see where your fuel trims and O2 voltages are at. A $30 Bluetooth dongle and Torque Lite will do that.

Check and make sure your intake is tight. Clean your IAC. Check for vacuum leaks.

Might want to try running it without the downpipe (front) O2 to rule out a plugged CAT.

-Mac

What would you make of all of this?

This jeep has already thrown me for 100 loops.

 

[bohuggabee]

Hey all.

I recently purchased a 2001 TJ 2.5l and was told it needed a fuel pump as it would randomly studder under load.

I replaced the fuel pump and both O2 sensors (NTK) last weekend. I decided to drive it Tuesday morning and it ran completely fine, parked for about an hour and then ran completely fine again to the next destination. No studder, idled fine, etc.

After work I went out to crank it and it immediately started spitting and studdering at idle and died. It did that multiple times so I ran it up to about 2k rpm's and the studdering stopped unless it went down to idle. I drove it home while keeping the rpm's up and luckily made it.

I performed a fuel pressure test and it jumps right up to 40-45lbs and leaks down if I don't crank it. Once I crank it, it stays around 40-50lbs at idle or when giving gas. At idle it just dies again.

Any help would be much appreciated.

Sounds just like mine. Its the return valve failing on the pump. This will act like a choke till it gets natural fuel pressure building. Im considering an external pump mod for mine. That i can then bypass and disconnect to keep the line pressurized when starting. My pump primes but it wont hold pressure in the line till its running. Then i can build pressure and keep it as the pump is running consistently. Worst thing about a tj. The fuel pumps are junk.

You can test it by parking on a downward incline so gravity resists the fuel line negative pressure after it primes. Since itll still start the pump does work. But that still has pressure and negative pressure. Once it starts. The engine is drawing fuel and the pump is just basically cycling.

So what do you do? Like i said. Just get an external pump. My mod is something i have to invent actually. But its just splicing in a return valve and a bypass system basically. So i can control it instead of the cpu. Which is just a choke. Older cars had chokes... this was one way to keep an engine from extra fuel or to allow it to warm up before full fuel pressure. And higher torque engines with carbs needed that input from the driver

 

[NoleyPoley807]

Sounds just like mine. Its the return valve failing on the pump. This will act like a choke till it gets natural fuel pressure building. Im considering an external pump mod for mine. That i can then bypass and disconnect to keep the line pressurized when starting. My pump primes but it wont hold pressure in the line till its running. Then i can build pressure and keep it as the pump is running consistently. Worst thing about a tj. The fuel pumps are junk.

You can test it by parking on a downward incline so gravity resists the fuel line negative pressure after it primes. Since itll still start the pump does work. But that still has pressure and negative pressure. Once it starts. The engine is drawing fuel and the pump is just basically cycling.

So what do you do? Like i said. Just get an external pump. My mod is something i have to invent actually. But its just splicing in a return valve and a bypass system basically. So i can control it instead of the cpu. Which is just a choke. Older cars had chokes... this was one way to keep an engine from extra fuel or to allow it to warm up before full fuel pressure. And higher torque engines with carbs needed that input from the driver

I already changed the fuel pump and it us working properly.